Search

Single wall carbon nanotubes (SWCNTs) are versatile building blocks for biosensors. Their near infrared (NIR) fluorescence enables detection of biomolecules in the optical tissue transparency window. The fluorescence intensity of SWCNTs changes in response to an analyte and this interaction can be chemical tailored by the surface chemistry. However, optical signals based on intensity are affected by external factors such as sample movement or fluctuations in excitation light. Here, we demonstrate fluorescence lifetime imaging microscopy (FLIM) of SWCNT-based sensors in the NIR as calibration-free method. For this purpose, we tailored a confocal laser scanning microscope (CLSM) for NIR signals (>800 nm) and employed time correlated single photon counting (TCSPC). (GT)10-DNA functionalized SWCNTs are then used as sensors because they increase their fluorescence (995 nm) in response to the important neurotransmitter dopamine. Their fluorescence lifetime (> 900 nm) follows a biexponential decay and the longer lifetime component (370 ps) changes with dopamine concentration. It increases by up to 25 % with detection limits in the nM range. These sensors serve as paint to cover cells and report extracellular dopamine in 3D via FLIM. We therefore show the potential of using fluorescence lifetime in combination with confocal microscopy as readout for SWCNT-based sensors.

Single-walled carbon nanotubes (SWCNTs) are versatile near infrared (NIR) fluorescent building blocks for biosensors. Their surface is chemically tailored to respond to analytes by a change in fluorescence. However, intensity-based signals are easily affected by external factors such as sample movements. Here, we demonstrate fluorescence lifetime imaging microscopy (FLIM) of SWCNT-based sensors in the NIR. We tailor a confocal laser scanning microscope (CLSM) for NIR signals (>800 nm) and employ time correlated single photon counting of (GT)₁₀-DNA functionalized SWCNTs. They act as sensors for the important neurotransmitter dopamine. Their fluorescence lifetime (>900 nm) decays biexponentially and the longer lifetime component (370 ps) increases by up to 25 % with dopamine concentration. These sensors serve as paint to cover cells and report extracellular dopamine in 3D via FLIM. Therefore, we demonstrate the potential of fluorescence lifetime as a readout of SWCNT-based NIR sensors. in press

Adipose-derived stem cells (ASCs) are an abundant and easily accessible multipotent stem cell source with potential application in smooth muscle regeneration strategies. In 3D collagen hydrogels, we investigated whether sustained release of growth factors (GF) PDGF-AB and TGF-β1 from GF-loaded microspheres could induce a smooth muscle cell (SMC) phenotype in ASCs, and if the addition of uniaxial cyclic stretch could enhance the differentiation level. This study demonstrated that the combination of cyclic stretch and GF release over time from loaded microspheres potentiated the differentiation of ASCs, as quantified by protein expression of early to late SMC differentiation markers (SMA, TGLN and smooth muscle MHC). The delivery of GFs via microspheres produced large ASCs with a spindle-shaped, elongated SMC-like morphology. Cyclic strain produced the largest, longest, and most spindle-shaped cells regardless of the presence or absence of growth factors or the growth factor delivery method. Protein expression and cell morphology data confirmed that the sustained release of GFs from GF-loaded microspheres can be used to promote the differentiation of ASCs into SMCs and that the addition of uniaxial cyclic stretch significantly enhances the differentiation level, as quantified by intermediate and late SMC markers and a SMC-like elongated cell morphology.